The petroleum and refinery industries use a large number of shut-off valves for controlling flow of liquid and gas products. An earlier retractable seal valve is illustrated in U.S. Pat. No. 2,977,086, Heinen; this valve is closed by a sequential motion including a downward vertical movement of a wedge-slip assembly to a position between inlet and outlet ports of the valve, followed by a horizontal movement of the sealing slips into engagement with the respective adjacent valve seats. The open position is achieved by a reverse sequential movement, wherein the slips are moved at a right angle away from the respective port seats and thereafter, the wedge-slip assembly is moved in an upward vertical movement away from the fluid passageway of the valve.
The valve of this type, perhaps because of its sequential opening and closing motions and complexity of parts, requires a stringent engineering design to assure realiability and trouble free operation. The improved valve of the invention provides an efficient perpendicular pull-off of the sealing slips from the port seats of the valve with absence of seal abrasion and wear. The structure of the invention provides positive locking of the sealing slips away from the wall of the valve body while the wedge-slip assembly is being moved. This is accomplished by an arrangement which forestalls movement of slips towards the body wall until the sealing slips are aligned with the valve ports.